(On October 7, 2012, this 1958 painting was defaced by a male visitor while on view at the Tate Modern in London. The man, later identified as a Russian artist named Vladimir Umanets, used a marker pen to tag the work, writing, “Vladimir Umanets ‘12 / a potential piece of yellowism.” As a witness at the scene tweeted “This guy calmly walked up, took out a marker pen and tagged it. Surreal.”

Umanets later told Britain’s Press Association news agency that he’d defaced the work in order to draw people’s attention to Yellowism, an artistic movement he’d co-founded, and compared his act to previous gestures from art history: “I didn’t destroy the picture. I did not steal anything. There was a lot of stuff like this before. Marcel Duchamp signed things that were not made by him, or even Damien Hirst.”

He also said he believed that his act had increased the painting’s value. “I believe in what I am doing and I want people to start talking about this. It was like a platform,” he said. “I didn’t decrease the value, I didn’t destroy this picture, I put something new.”)